Gas turbine air storage system

ABSTRACT

Gas turbine air storage system with subterranean air storage space, for example, in a cavern formed in a salt stratum to which a bore hole extends, includes a plurality of tubes including an outer protective tube extending through the bore hole into the air storage space, a lining for the bore hole spaced from and surrounding the outer protective tube, the lining and the outer protective tube defining therebetween an annular space communicating with the air storage space, and means for feeding air to the air storage space at least partly through the annular space.

United States Patent Schwarz Mar. 12, 1974 [54] GAS TURBINE AIR STORAGESYSTEM 2,928, 11 I 3/1960 Johnson 137/236 2,787,455 4/1957 Knappen...61/.5 X [75] Inventor Theodor Erlangen, 3,108,438 10/1963 Harvey 137/236x Germany 3,538,340 ll/l970 Lang 290/52 [73] Assignec: Kraftwerk UnionAktlengesellschait,

Mulheim (Rhur), Germany Primary Examiner-Clarcncc R. Gordon Filed p 51972 Attorney, Agent, or FirmHerbert L. Lerner Appl. No.: 241,300

[30] Foreign Application Priority Data Apr. 6, 1971 Germany P 21 I6850.3

m (is. er". 5159.29, 61/.5, 137/236, 290/52 [51] Int. Cl. F02c 9/14 [58]Field of Search 60/3929, 39.23; 137/236;

[56] References Cited UNITED STATES PATENTS 3,355,893 l2/l967 Kuhne 61/5Gas turbine air storage system with subterranean air storage space, forexample, in a cavern formed in a salt stratum to which a bore holeextends, includes a plurality of tubes including an outer protectivetube extending through the bore hole into the air storage space, alining for the bore hole spaced from and surrounding the outerprotective tube, the lining and the outer protective tube definingtherebetween an annular space communicating with the air storage space,and means for feeding air to the air storage space at least partlythrough the annular space.

ABSTRACT I 10 Claims, 3 Drawing Figures PAIENTEDHAR 12 I974 5 Flg 1 2PRIOR ART GAS TURBINE AIR STORAGE SYSTEM The invention relates to a gasturbine air storage sys-- tem with a subterranean air storage space orreservoir, particularly in a salt cavern formed in a salt stratum. Inthe installation for such a system, a bore hole extends to the airstorage space and is provided with a casing provided with severalsprings. An annular space is defined between the casing and thesurrounding rock through which the hole is bored, and is usually filledwith cement, it being important that an absolutely airtight seal beprovided. The air riser tube can then be suspended within'the bore holelining, and serves as a protective tube for the lining when the cavernis flushed.

For stored gaseous media, the annular space between the bore hole liningand the riser tube string is closed off by a so-called packer in thelower part of the bore hole, and the annular space thereabove is filledwith a protective liquid. In this manner, adequate protection againstcorrosion of the casing is attained in that region of the bore hole.

In air storage spaces or reservoirs, the protective liquid can assume,in addition to protection against corrosion, the additional function ofthermal insulation against temperature variations of the stored air, aslong as the packer does not provide a thermal bridge of anysignificance. If the stored air is withdrawn relatively rapidly foroperation of the gas turbine, the state of the stored air changesadiabetically, i.e., a temperature decrease takes place simultaneouslywith a reduction in pressure. When compressor air is fed into thestorage I space, the change of state of the enclosed residual airquantity takes place in reverse, but generally more slowly. Because ofthe difference in thermal expansion and thermal conduction between thebore hole casing and the surrounding rock as well as the mass ofconcrete, the operational temperature variations in the bore hole liningmust stay within given limits that are relatively narrow because,otherwise, development of leaks must be anticipated.

The application of ring-shaped sealing elements, i.e., the so-calledpacker with an outside diameter of half of a meter, for example, inshafts having a length of 500 m and more, required a large commercialand technical expenditure. Furthermore, in the case of great pressuredifferences, a tight seal for the protective liquid contained in theannular space located above the packer must be assured. The sealingeffect of a packer installed in this manner can become questionable whenthe air pressure varies, especially when there is a temporary totalwithdrawal of the air.

The disadvantage must, however, always be taken into consideration thatthe tube sections located below the packer have no protection againstcorrosion since they are subject to condensation of humidity or airmoisture which occurs when the pressure drops due to the withdrawal ofair. This condensation, in conjunction with the deposition of saltparticles from the caverns, forcibly result in intensive corrosion ofthe exposed tube sections.

It is accordingly an object of the invention to provide a gas turbineair storage system which avoids the foregoing disadvantages of theheretofore known systems of this general type.

With the foregoing and other objects in view, there is provided, inaccordance with the invention, gas turbine air storage system withsubterranean air storage space, for example, in a cavern formed in asalt stratum to which a bore hole extends, comprising a plurality oftubes including an outer protective tube extending through the bore holeinto the air storage space, a lining for the bore hole spaced from andsurrounding the outer protective tube, the lining and the outerprotective tube defining therebetween an annular space communicatingwith the air storage space and means for feeding air to the air storagespace at least partly through the annular space.

By means of this invention, it is possible to dispense with the packeror similar sealing elements entirely, since the supply of air into thestorage space or reservoir takes place at least partly in the annularspace defined by the protective tube and the bore hole lining.

In accordance with another feature of the invention, air feeding meansare provided for feeding, for example, a partial flow of the combustionair as fresh air into the annular space even during useful outputoperation of the gas turbine, so that corrosion protection of the entirelength of tube is assured. If, therefore, a partial stream of compressedfresh air is fed from above into the annular space even when air isbeing withdrawn from the air storage space for turbine operation, andthereby a downward flow of air is continuously maintained in the entireannular space, no condensation of air moisture can take place therein,so that no corrosion can therefor occur.

As the accompanying air flows down into the storage space or reservoir,a considerable part of the heat is absorbed by this air and istransferred from the rising combustion air to the riser tube. The risertube has additionally been provided on the inner surface thereof with asuitable protective layer for protection against corrosion such as aplastic lining, for example, the lining being simultaneously effectiveas thermal insulation.

When the operation is exclusively in the compressor mode, all or part ofthe fresh air supply flows through the annular space into the storagespace or reservoir, so that during the densification of the enclosedair, an upwardly directed flow in the annular space is reliablyprevented. Air moisture or humidity and salt particles from the storagespace or reservoir can therefore not penetrate into the annular spaceand cannot precipitate or condense at the tube walls.

The temperature of the fresh air can be controlled in order to conformto the temperature of the surrounding rock in which the bore hole isformed. By admixing with the air, a medium to protect against corrosionprior to extended idle periods of the gas turbine, the possibility isafforded of protecting the walls of the annular space against rusting.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin gas turbine air storage system, it is nevertheless not intended to belimited to the details shown, since various modifications and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments, whenread in connection with the accompanying drawings, in which:

FIG. I is a diagrammatic sectional view of a gas turbine air storagesystem known in the prior art;

FIG. 2 is a view corresponding to that of FIG. 1 of an embodiment of theinvention of the instant application; and

FIG. 3 is an enlarged diagrammatic view of the upper part of FIG. 2showing a modification thereof.

Similar parts in each of the figures are identified by the samereference numerals.

Referring now to the drawing, and first particularly to FIG. 1 thereof,there is shown in the prior art system a subterranean storage space orreservoir 1 in the form of a cavern or cavity present in a salt stratumin the earth, the cavern being connected by a bore hole 2 to the groundsurface 3. The bore hole 2 is provided with an inner lining 4, and acement filling is provided in the annular space between and defined bythe bore hole lining 4 and the rock surrounding 5 in which the bore hole2 is formed. A protective tube 6 extends through the bore hole 2 intothe air space cavern 1 and is used as an air riser tube during theoperation of the gas turbine air storage system. As shown in the priorart representation of FIG. 1, a ring-shaped seal in the form of apacking or a so-called packer 7 has been provided heretofore with aprotective liquid 8 located thereabove.

As FIG. 2 shows, in contrast to the prior art system of FIG. 1, thepacker has been dispensed with because the entire quantity of air, orpart thereof, is now passed into the hollow space or reservoir 1 throughan annular space 9 located between the protective tube 6 and the borehole lining 4. Air enters into the annular space 9 in direction of thearrow 10 through a line 11 in which a stopcock or shut-off valve 12 isprovided, and flows downwardly in direction of the arrow 13. The storedair discharges in direction of the arrow 14 through the interior of theprotective tube 6 i.e. in the annular space 15 therewithin. The tube 6,which is used as the air riser tube, is provided with a protective heatinsulating layer on the inner surface thereof, which has the effect ofprotecting the tube 6 against corrosion. The stored air is conducted indirection of the arrow 18 to the gas turbine installation proper (notshown) through a line 16 provided with a shut-off valve 17. A tube 19,20 serves for elutriation or washing out the air reservoir 1, the saltwater and residual water being drawn off therethrough in direction ofthe arrow 21.

Whereas, in the embodiment of FIG. 2, the tubes 6 and 16 serving fordischarge of the stored air are traversed by the air flow only in upwarddirection, it is also possible to use these tubes 6 and 16 forfeeding-in the air to be stored or to have them participate in thisprocess, and thus to operate with a downward flow therethrough. Anexample of an embodiment operating in this manner is shown in FIG. 3. Asair is withdrawn through the protective tube 6 serving as the airwithdrawal tube, the air flows in direction of the arrow 18 through theline 16 provided with shut-off valves 17a and 17b, and subsequentlytravels through the line 23 to the non-illustrated gas turbineinstallation proper in direction of the arrow 24.

When storage air is supplied to the reservoir 1, it flows through thesame pipe 23, but now in direction of the arrow 25, the main flowtraveling with the shutoff valves 17a and 17b in open condition, indirection of the arrow 26 through the line 16 and the protective tube 6.A partial flow of the compressed air which is to be fed into the storagereservoir 1 passes through a check valve member 27 and the shut-offvalve 12, to the line 1 1, there the flow travels downwardly in theannular space 9 in direction of the arrow 10 to the storage reservoir 1.

The shut-ofi member 12 can, of course, be constructed as a controlvalve, in order to meter desirably the partial quantity of air flowingthrough it. The check valve 27 prevents, .when air is being withdrawn, aflow from rising in the annular space 9, which would mean danger ofcorrosion damage to the protective tube 6. The air riser tube istherefore always protected against corrosion, because it carries aprotective layer on inner surface thereof and is protected from a risingair flow at the outer surface thereof in the manner hereinbeforedescribed. It thus is possible, if desired, to force air in smallquantities into the annular space 9, as indicated by the arrow 28through an open shut-off valve 29, also when air is being withdrawn fromthe storage space 1, in order to reliably prevent, in conjunction withthe check valve 27, an upward flow in the annular space 9.

I claim:

1. Gas turbine air storage system with subterranean air storage space,for example, in a cavern formed in a salt stratum to which a bore holeextends, comprising a plurality of tubes including an outer protectivetube extending through the bore hole into the air storage space, alining for the bore hole spaced from and surrounding said outerprotective tube, said lining and said outer protective tube definingtherebetween an annular space therebetween communicating with the airstorage space, means for withdrawing air from said air storage spacethrough said protective tube, and means for feeding at least a partialflow of the air to said air storage space through said annular space assaid air is fed to the air storage space, thereby providing a downwardflow of air in said annular space to preclude corrosion in said annularspace.

2. System according to claim 1 wherein said means for withdrawing airfrom said storage space includes a tube located within said outerprotective tube in the bore hole and extending out of said protectivetube above ground and communicating with a gas turbine for supplyingcombustion air thereto from said subterranean air storage space duringuseful output operation of the gas turbine, said air feeding means beingoperable during the useful output operation of the gas turbine forfeeding a partial flow of fresh air through said annular space betweensaid bore hole lining and said protective tube to said subterraneanstorage space.

3. System according to claim 1 including a heatinsulating,corrosion-resistant lining disposed on the inner surface of saidprotective tube.

4. System according to claim 1 wherein said inner lining of saidprotective tube consists of synthetic resin.

5. System according to claim 1 including control means for maintainingthe temperature of the air fed into the subterranean storage space at avalue within the temperature limits of the ambient earth formation inwhich the air storage system is located.

6. System according to claim 1 including means for admixing metereddoses of corrosion-resistant medium to fresh air being fed fromabove-ground to the subterranean air storage space.

7. System according to claim 1 wherein said means for withdrawing airfrom said air storage space is also used for feeding air to said storagespace, said withdrawing and feeding means including a first conduitmeans in communication with said protective tube and extending out ofsaid protective tube, said first conduit means being in communicationwith a gas turbine for supplying combustion air thereto from saidsubterranean air storage space and in communication with a supply of airto be stored, said feeding means including a second conduit means incommunication with said annular space for feeding air to said annularspace and a third conduit means between said first conduit means andsaid second conduit means for directing a partial flow of air from saidfirst conduit means to said second conduit means as air is being fed tosaid storage tank through said first conduit means.

8. System according to claim 7 wherein said third conduit means includesa check valve permitting oneway flow from said first conduit means tosaid second conduit means. 7

9. System according to claim 7 wherein said third conduit means includesa control valve to meter the amount of partial flow of air beingdiverted from said first conduit means to said second conduit means.

10. System according to claim 8 wherein said second conduit means has apipe supplying air to said second conduit means, whereby air is fed tosaid annular space both through said pipe and through said check valvein said third conduit means.

1. Gas turbine air storage system with subterranean air storage space,for example, in a cavern formed in a salt stratum to which a bore holeextends, comprising a plurality of tubes including an outer protectivetube extending through the bore hole into the air storage space, alining for the bore hole spaced from and surrounding said outerprotective tube, said lining and said outer protective tube definingtherebetween an annular space therebetween communicating with the airstorage space, means for withdrawing air from said air storage spacethrough said protective tube, and means for feeding at least a partialflow of the air to said air storage space through said annular space assaid air is fed to the air storage space, thereby providing a downwardflow of air in said annular space to preclude corrosion in said annularspace.
 2. System according to claim 1 wherein said means for withdrawingair from said storage space includes a tube located within said outerprotective tube in the bore hole and extending out of said protectivetube above ground and communicating with a gas turbine for supplyingcombustion air thereto from said subterranean air storage space duringuseful output operation of the gas turbine, said air feeding means beingoperable during the useful output operation of the gas turbine forfeeding a partial flow of fresh air through said annular space betweensaid bore hole lining and said protective tube to said subterraneanstorage space.
 3. System according to claim 1 including aheat-insulating, corrosion-resistant lining disposed on the innersurface of said protective tube.
 4. System according to claim 1 whereinsaid inner lining of said protective tube consists of synthetic resin.5. System according to claim 1 including control means for maintainingthe temperature of the air fed into the subterranean storage space at avalue within the temperature limits of the ambient earth formation inwhich the air storage system is located.
 6. System according to claim 1including means for admixing metered doses of corrosion-resistant mediumto fresh air being fed from above-ground to the subterranean air storagespace.
 7. System according to claim 1 wherein said means for withdrawingair from said air storage space is also used for feeding air to saidstorage space, said withdrawing and feeding means including a firstconduit means in communication with said protective tube and extendingout of said protective tube, said first conduit means being incommunication with a gas turbine for supplying combustion air theretofrom said subterranean air storage space and in communication with asupply of air to be stored, said feeding means including a secondconduit means in communication with said annular space for feeding airto said annular space and a third conduit means between said firstconduit means and said second conduit means for directing a partial flowof air from said first conduit means to said second conduit means as airis being fed to said storage tank through said first conduit means. 8.System according to claim 7 wherein said third conduit means includes acheck valve permitting one-way flow from said first conduit means tosaid second conduit means.
 9. System according To claim 7 wherein saidthird conduit means includes a control valve to meter the amount ofpartial flow of air being diverted from said first conduit means to saidsecond conduit means.
 10. System according to claim 8 wherein saidsecond conduit means has a pipe supplying air to said second conduitmeans, whereby air is fed to said annular space both through said pipeand through said check valve in said third conduit means.